Analog/Digital Inputs; Thermocouple; Resistance Thermometer (Rtd) - ABB SM500F User Manual

Field Mountable Videographic Recorder
SM500F

2.4 Analog/Digital Inputs

2.4.1 Thermocouple – Fig. 2.9
Use the correct compensating cable between the thermocouple and the terminals – see Table 2.1 on
page 17.
Automatic cold junction compensation (ACJC) is incorporated but an independent cold (reference) junction
may be used.
2.4.2 Resistance Thermometer (RTD) – Fig. 2.9
On applications requiring long leads it is preferable to use a 3-lead resistance thermometer.
If 2-lead resistance thermometers are used, each input must be calibrated to take account of the lead
resistance.
1 2 3 4
+ —
Voltage
1 2 3 4
3-lead RTD
In the powered-down condition the current input
*
is open circuit. In order to maintain a current loop
when the unit is powered down, fit a zener diode
(BZX79 — B/C2V4) to the input as shown.
Fig. 2.9 Analog/Digital Input Connections
Note. Analog/digital input terminal screws must be tightened to a torque of 0.5 Nm (4.5 lbf.in).
16
Each lead must be of equal
resistance and less than 10Ω
1 2 3 4
—
*
Current
1 2 3 4
4-lead RTD
2 Installation
1 2 3 4
—

Thermocouple

1 2 3 4
—
Logic state inactive
Logic state active
Digital Input
(Volt free or 24V)
IM/SM500F Issue 10.1